Generally speaking, backlight modules with various of structures are used to enhance the brightness of backside illumination flat-panel displays, such as liquid crystal displays (LCDs) including not only electronic illumination boards, notebook computer displays, word processors, desktop computer displays, television sets, camcorders, but also displays of vehicles and aircrafts. The backlight module is equipped with a light source, a light guide plate and a plurality of optical sheets, and light from the light source exits to the display after passing through the light guide plate and the plurality of optical sheets.
FIG. 1 is a schematic view summarily illustrating a prior-art backlight module. As shown in FIG. 1, the backlight module includes a light source 4; a light guide plate 5 for changing the path of light exiting from the light source 4 to guide the light to a display (not shown in the figure); a plurality of optical sheets 6, 7, 8 disposed between the light guide plate 5 and the display (not shown in the figure) to enhance the efficiency of light exiting from the light guide plate 5; a reflecting plate 2 disposed below the light guide plate 5 to prevent light produced by the light source 4 from being exposed to the outside; a light source reflecting plate 3; and a modular frame 1, on which are sequentially stacked the reflecting plate 2, the light source reflecting plate 3, the light guide plate 5 and the optical sheets 6, 7, 8.
During the process of fabrication, the optical sheets 6, 7, 8 may consist of a diffusion sheet 6, a prism sheet 7 and a protection sheet 8, wherein the diffusion sheet 6 serves to diffuse light exiting from the light guide plate 5 and being incident on the display (not shown in the figure), to thereby make uniform luminance distribution of the light. Repetitive prisms each having a triangular cross-section are repeatedly formed on the upside of the prism sheet 7, to thereby concentrate the light diffused by the diffusion sheet 6 to a direction perpendicular to the plane of the display (not shown in the figure), so as to enhance the brightness.
Accordingly, the light going through the prism sheet 7 mostly proceeds perpendicularly relative to the plane of the display (not shown in the figure), whereby to have uniform luminance distribution. Additionally, the protection sheet 8 is stacked on the prism sheet 7 to diffuse light incident through the prism sheet 7 at the same time of protecting the surface of the prism sheet 7, so as to make uniform distribution of the light.
It is found by careful observation of the optical sheets, particularly of the diffusion sheet, that, with the recent tendency of LCDs such as lightweight, ultrathin and highly bright and increased use of LED lamps, there is a need to obtain a diffusion sheet with diffusing effect and without loss of luminance while concealing the arrangement mode of lamps.
Relevant thereto, the prior-art microlens is formed by arranging a single layer of semispherical patterns into a column by means of a UV adhesive, but the prior-art technology fails to conceal the haze of the arrangement mode of the LED lamps at the same time of avoiding loss of luminance.
U.S. Pat. No. 7,160,018 discloses a backlight system for forming a nano-particle layer at a micro-thin structural surface of a light guide plate. The patent attempts to improve luminance of light supplied to a liquid crystal display device by virtue of a nano-particle layer disposed on the surface of the light guide plate. This prior-art technology is problematic in the fact that it is relatively difficult to uniformly apply the nano-particle layer on the surface of the light guide plate, which is made of a hard material, as this is achievable only by such means as chemical deposition.
Other prior-art technologies are so restricted as to only supply nano-particles inside the light guide plate or inside the micro-thin structural surface of the lens, and there is hence still a problem of being easily scratched due to contact between other optical sheets and the protection sheet.
It is therefore needed to obtain a micro-molded sheet having certain rigidity and the property against distortion or bending at the same time of guaranteeing transmissivity and the diffusing effect, and enhancing haze and concealing performance to reduce loss of luminance.